Pressure maintaining mechanism



Dec. 29, 1931. 1. LUNDGAARD PRESSURE MAINTAINING MECHANISM Filed Aug 5, 1926 J v S.

Patented Dec. 29, 1931 UNITED STATES PATENT OFFICE IVAR LUNDGAAlR-D, OF WORCESTER, MASSACHUSETTS, ASSIGNOB TO DEVON MANU- FACTURING COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSA- CHUSETTS PRESSURE MAINTAINING MECHANISM Application filed August 5, 1926.

This invention relates to an improvement in air refrigerating apparatus and more particularly to means adapted to provide and maintain the mediating air at a pressure considerably higher than the outer or atmospheric pressure and in combination therewith to retain a suitable quantity of lubricating oil in the machine. In general this invention relates to air refrigerating 9 apparatus disclosed in my prior Patent No.

1,240,862 of September 25, 1917 and in some respects comprises an improvement upon the subject matter disclosed in my copending application No. 691,165 filed February 27, 19:24:. In apparatus of the general type disclosed in the above-identified patent and application, a constant quantity of mediating fluid, such as air, is alternately expanded and compressed in order to provide refrigeration.

The refrigerating efliciency of a machine of given size will be greater if the air density is increased since the ability of the air within the machine to give up or absorb heat is proportional to its mass, provided that the capacity of the means for conducting heat to and from the air or machine is not exceeded. The heat absorbing and delivering capacity of the passages in the heat exchangers and the interchangers will also increase substan- 30 tially in proportion to the increased density of the air, so that, provided suitable means is provided to conduct heat into and out of the machine, a given size of machine will be more efficient ifthe average pressure is 5 increased, or, when a given refrigerating capacity is necessary, the provision of a smaller and more compact refrigerating machine will be possible, if the mediating air is a higher average pressure than the atmospheric pressure. For example, according to experience and data now collected I have found that it is expedient to employ a pressure of from two to three atmospheres; Furthermore, the provision of a smaller refrigcrating machine results in the reduction of weight of the reciprocating and rotating parts, and consequently their inertias and centrifugal'forces, thus reducing the amount of vibration and noise; and the use of a comparatively small and compact machine also Serial No. 127,294.

results in reduction of friction losses and a lower cost of production.

In order to provide satisfactory operation in refrigerating apparatus of this character it is necessary to keep the air dry in order to prevent the formation of frost in the air ducts and their consequent stoppage. It is, therefore, highly desirable to maintain a constant body of air under pressure within the machine so that, after the air hasonce been dried, it will not be necessary to make use of a drying medium, such as a moisture absorbing chemical, in order constantly to dry a new charge of air. The present invention discloses improved means for building chine with lubricating oil, such means being designed and arranged so that there is very little necessity of replenishing either the ai or oil supply.

Referring more particularly to specific structural details embodied in the present- "invention, it pertains first to a make-up pump to supply air to the refrigerating machine both for building up the initial pressure to the desired amount and for making up for any slight leakage of air which may occur, this pump also serving to maintain a suitable supply of oil in the crank case of the machine. The invention further pertains to means for conserving or recovering oil that may tend to leak from an oil seal provided for the crank shaft of the machine, which seal is adapted to cooperate with the make-up pump in maintaining the desired internal air pressure.

The above and further objects and advantageous structural features of the invention will become apparent to those skilled in the ,art upon a reading of the subjoined description and claims in conjunction with the accompanying drawings in which Fig. 1 is a view partly in section and partly in elevation of a refrigerating machine embodying one specific form of the invention; Fig. 2 is a view partly in section and partly in side elevation of a part of the machine; and

Fig. 3 is a detailed sectional view; and

Fig. 4 is a section on line 1-4 of Fig. 1.

Referring to the accompanying drawings, the numeral 1 represents the crank case of a refrigerating machine as of the general character disclosed in my prior Patent No. 1,240,- 862 and comprising compression and expansion chambers provided with an upstanding cylinder 2 and containing a compression piston 3 and a shifter piston 4, between which the air is compressed, thereupon passing through heat exchangers 7 and 8 and inter-- changer 9 to the head of the cylinder which comprises the expansion chamber. Suitable mechanism such as the crank shaft 10, the connecting-rod 11, link 12, bell crank 13, and links 14 are arranged to reciprocate the two pistons 3 and 4 in properly synchronized relation.

At the bottom of the crank case a suitable cover plate 14 is held in substantially oil tight engagement with the crank case by fastenings 15, and below this plate is an oil sump 16 designed to receive any leakage of oil about cover plate 14 and to be open to atmospheric pressure. Sump 16 is provided -with a suitable filler 18 and drain plug 19 by :means of which the oil may be renewed from "time to time when its lubricating qualities the motor end. About the extension 23 is disposed suitable ring packing 24' of fibrous or compressible material between laminations of which is a lanterngland 26 which is connected with the oil chamber by a suitable duct 27. Duct'27 permits the flow of oil about the gland 26 which has a comparatively loose fit on the shaft and serves to maintain 'an oil seal at this point; Packing 24 is retained'in firm engagement with the shaft by the coil spring 29, which bears on the washer -57, and on the washer 28 which engages with the ball bearing 290 located adjacent tothe outermost-part of the motor end. A boss 30 extends from theccntral part of the motor "endand forms a chamber aboutthe coil spring which is adapted to receive any leakage of lubricant passing by the packing 24-. A suitable pipe 31 leads downwardly from this chamber to sump 10 in order to return "the oil to the sump and to prevent its wastage. Any suitable part of the-operating mechanism for the pistons may beconnected'with the plunger l6 of the make-up pump, as, for example, in the present case the bell crank 13 is connected by the link 47 with the plunger 46. The body of the pump comprises an upstanding substantially tubular casing 01' cylinder 45 which has a base 48 which may be bolted or secured in any suitable manner to the cover plate at the bottom of the crank case. The plun er 46 is provided with a suitable pipe 10 extending downwardly somewhat below its bottom and connected with a trans verse passage 39 intermediate its length. The cylinder of the pump is provided with a port 38 which is adapted to register with the pars sage 39 when the plunger is the bottom of its stroke and is also provided with a port 37 adapted to be uncovered by the plunger, at the top of its stroke. Port 37 is connected with a downwardly extending pipe 40, the lower end of which is located in the sump and is surrounded by a strainer 41 for removing small particles and impurities from the oil. Above the strainer 41 the duct 40 has a substantially horizontal branch 44, the end of which preferably extends upwardly along the side of the m achincand terminates in a suitable dryer 50. Dryer 50 comprises a vessel containing a, suitablemoisture absorbing chemical such as calcium chloride, phosphoric acid, phosphoricpentoxide or the like and'has a-suitableopening 56 into the outer air. The cham ber within the cylinder has an extension 49. formed by a recess in the cover plate in order to comprise a suitable vacuum or clearance chamber 98. The vacuum chamber is connected by a short duct 51 with the ball check valve 52 located on the base plate 48.

It may be seen that in the operation of my machine the sump is provided with oil which .15 pumped upwardly by the reciprocating plunger 46, upward movement of which creates a vacuum in, the vacuum or clearance chamber and draws oil in through the duct and then forces it out through the port 38 into the crank case upon the downward movement of the plunger. Since oil is relatively non-compressible, it is necessary to provide the relief valve 52 in order to permit the flow of oil through the duct 51, when conditions of pressure within the vacuum chamber necessitate, and thus to maintain a substantially constant clearance in the vacuum chamber. The oil will continue to be forced into the crank case until its level in the sump has fallen to a position even with the horizontal pipe whereupon the pump will tend to draw air inwardly through the dryer 50, compressing the air in the vacuum chamber, until the passage 39 registers with the port 38 when the air may escape into the crank case.

It is thus evident that the pressure in the vacuum chamber determined by the relative maximum and minimum volumetric capacities of the clearance orvacuum chamber of the pump will determine the air pressure which will be built up Within the crank case. Since it is impossible to make the pistons 3 and 4 air tight, leakage of air through the piston of the crank case will eventually result in the same average air pressure in various parts of the machine, this air pressure being determined by the maximum and minimum volumes of the vacuum chamber.

' When the initial pressure of the machine has been built up to this point, ordinarily no air will be pumped in by the pump since the air pressure within the vacuum chamber at the instant of the maximum compression will exactly balance the interior pressure within the crank case of the machine and under these conditions the plunger will merely reciprocate, alternately compressing and expanding air in the vacuum chamber. However, if slight leakage of air occurs as, for example, about the stuffing box at the crank shaft 10, the pump 45 will automatically make up the difference in pressure and maintain the pressure at the desired point. A machine of this type in most installations is normally subcct to operation from one third to two thirds of the time and during periods of idleness j some air: leakage may take place but this will be made up in a few revolutions of the crank shaft and movements of the make up pump when the machine starts running at the end of the idle period. When overflow of oil through pipe 31 causes the sump to be filled above the level of the pipe, oil rather than air is pumped into the crank case until the oil level in the sump falls to the level of the horizontal pipe.

It is evident that I provide means for automatically retaining the desired air pressure in a reg'frigerating machine provided with pistons and that I have combined therewith means for retaining the oil in the crank case at a desired level and at the same time permitting replenishment of the oil without opening the interior of the machine to atmospheric pressure. Ordinarily a sufficient amount of oil will be contained in the crank case to permit lubrication of all parts by splash due to the dipping of the crank throw and the connecting rod end into the oil, and thus an oil seal is normally provided about the pump 45 as well as about the crank shaft 10. l Vhile I have disclosed in the preferred form of my invention the pump actuating means connected to a bell crank it is obvious that many other equivalent actuating mechanisms may be provided to obtain a similar result.

I claim:

1. Apparatus for maintaining a predetermined average air pressure within the easing of a machine, comprising an air pump having a clearance chamber therein, a re ciprocating piston to vary the volume of said chamber, said chamber being provided with two ports which communicate with the interior of the machine and the outer air respectively, one of said ports being uncovered by the piston near each end of its stroke and being covered thereby during the remainder of its movementand a duct connecting said chamber with the interior of said casing and a. check valve located in said duct.

2. Apparatus for maintaining a predetermined tluid pressure within the casing of a machine, comprising a reciprocating plunger and a cylinder providing a clearance chamber, the -'all of the cylinder having a port communicating with the source of fluidsupply outside the casing and a second port communicating with the interior of the easing, the plunger uncovering the first-named port near its outer position in relation to the clearance chamber and being provided with an internal passage communicating with said chamber and adapted to register with the second-named port near'the opposite end of ber.

3. Combined means for maintaining a predetermined gaseous pressure within the casing of a machine and for supplying the ma chine with lubricating oil, said means comprising a pump provided with a cylinder and a reciprocating plunger, a source of oil supply outside said casing, the wall of the cylinder having a port communicating with said source of oil supply and also serving as an inlet for gas and a second port adapted to communicate with a passage in the interior of the plunger, said plunger being reciprocahle to provide a smaller orlarger clearance chamber within the cylinder and uncovering the first-named port near the position of largest clearance chamber volume and uncovering the second-named port'near theposition of smallest clearance chamber volume and covering said ports during the remainder of its stroke, and auxiliary means permitting" the escape of oilunder pressure from said chamber.

4. Combined means for maintaining a predetermined gaseous pressure within the easing of a machine and for supplying the mathe wall of the cylinder having a port communicating with said reservoir and also servas an'inlet forigas and a second port adapted to communicate with the interior cable toprovide a smaller or larger clearance the plunger stroke, said passage having an' of the plunger, said plunger being reciprochamber within the cylinder and uncovering the first-named port near the position of largest clearance chamber volume and uncovering the second-named port near the position of the smallest clearance chamber vol ume and covering said ports during the remainder o f its stroke, the oil and gas inlets to the pump being so arranged that they may draw oil into the casing when the level in the reservoir has reached a predetermined height and may draw gas into the machine when the oil level is below said predetermined height and the internal pressure within the machine below a predetermined amount.

5. Combined means for maintaining a predetermined gaseous pressure within the easing of a machine and for supplying the machine with lubricating oil, said means comprising. a pump provided with a cylinder and reciprocating plunger, a source of oil supply outside said casing, the wall of the cylinder having a port communicating with said source of oil supply and also serving as a gas inlet and a second port adapted to communicate with the interior of a plunger, said plunger being reciprocable to provide a smaller or larger chamber within the cylinder and being provided with an internal passage communicating with the interior of the cylinder and registering with the first-named port only near the upper part of its stroke and uncovering the last-named port casing near the other extremity of its stroke and covering' said ports during the remainder of its stroke, and auxiliary means permitting the escape of oil under pressure from said cylinder;

6. Means for maintaining a predetermined degree of gaseous pressure within the casing of a machine and to supply said casing with lubricating oil, said means comprising an oil and gas pump having an outlet within the casing, a receptacle for containing oil, and an inlet communicating with said receptacle to supply oil to the pump and being arranged to serve as a gas inlet to the pump when the oil in the receptacle falls below a predetermined level.

7. Means to maintain a predetermined degree of gaseous pressure within the casing of a machine and to supply said casing with lubricating oil comprising a sump below the casing of the machine adapted to receive oil leakage therefrom, and a pump having an outlet within said casing and an inlet communicating with said sump and also serving as a gas inlet when the oil within the sump falls below a predetermined level.

8. Means to maintain a predetermined degree of gaseous pressure within the casing of a machine and to supply said casing with lubricating oil comprising an oil sump below the casing of the machine, an oil and gas pump having an outlet within said casing and an inlet communicating with said sump,

a substantially horizontal duct serving as a gas inlet and located within said sump and communicatingjwith said first-named inlet, therise of the oil level above said duct shutting ott the flow of gas whereupon the pump will draw oil from the sump into the machine.

9. Means to maintain a predetermined degree of gaseous pressure within the casing of amachine and to supply said casing with lubricating oil comprising a pump having an outlet within the casingand an inlet, a source of oil supply including an oil sump below the casing of the machine, and a conduit connected to said inlet and extending into said sump, said conduit having a branch with a substantially horizontal portion which serves as a gas inlet and having an end terminating in said sump below the level of the oil therein, whereby rise of the oil level above the horizontal branch portion will shut off the'source of gas supply from the inlet.

10. Mechanisms to maintain a predetermineddegree of gaseous pressure within the casing of a machine and to supply said casing with lubricating oil comprising means for inducing movement of fluid into the casing, an oil reservoir, said means being provided with an inlet duct having an opening within said reservoir serving as a gas inlet and covered by the rise of oil above a certain level within the reservoir.

11. The combination of mechanism for maintaining a predetermined gaseous pressure within the casing of a machine and for retaining a suitable oil supply within the machine comprising a pump for maintaining the gaseous pressure, a shaft projecting from the machine, an oil sealed hearing about said projecting shaft to minimize gaseous leakage, means for collecting the seepage of oil forced out of said bearing due to gaseous pressure, and means for returning said oil to interior of the casing of the machine.

12. The combination of mechanism for maintaining a predetermined gaseous pressure within the casing of a machine and for retaining a suitable oil supply within the machine comprising a make-up pump for maintaining the gaseous pressure, a shaft projecting from the machine, an oil sealed bearing about said projecting shaft to minimize gaseous leakage, means for collecting the seepage of oil out of said bearing due to gaseous pressure, and means for returning said oil to the interior of the casing of the machine, said last-named means comprising a sump below the casing, the make-up pump having a passage extending into the sump and being effective to draw oil above a given level out of the sump.

13. The combination of mechanism for maintaining a predetermined gaseous pressure within the casing of a machine and for retaining a suitable oil supply within the machine comprising a make-up pump for supplying the casing with gas and oil, a shaft projecting from the machine, an oil sealed hearing about said projecting shaft to minimize gaseous leakage, means for collecting the seepage of oil out of said bearing due to gaseous pressure, and means whereby the make-up pump may return the collected oil to the interior of the casing.

14. The combination of mechanism for maintaining a predetermined gaseous pressure Within the casing of a machine and for retaining a suitable oil supply within the machine comprising a make-up pump for supplying the casing with gas and oil, a shaft projecting from the machine, an oil sealed bearing about said projecting shaft to minimize gaseous leakage, means for collecting the seepage of oil out of said bearing due to gaseous pressure, and an oil reservoir open to the atmosphere, and a duct for draining the collected oil into said reservoir, said pump returning the oil from the reservoir to the casing.

15. The combination with a machine having a casing adapted to contain lubricating oil and a shaft extending from the interior of the casing to the outside of the machine, of an oil sump below said casing, means to conduct oil leaking from the casing along said shaft to said sump, a pump having an outlet within said casing and an inlet, a duct connecting said inlet with said sump and open to the atmosphere above the bottom thereof, whereby the pump will be eifective to pump oil from the sump to the casing whenever the oil level in the sump is above the part of the duct open to the atmosphere.

Signed by me at Boston, Massachusetts, this 2nd day of August, 1926.

IVAR LUNDGAARD. 

